To the arid side of the chernozem belt lies the belt of chestnut soils or dark brown soils. They occupy the semiarid middle-latitude steppe lands, in North America and Asia. The chestnut-soil profile is generally similar to the chernozem, but contains less humus and hence is not so dark in colour. The soil structure tends to be prismatic in the B-horizon.
The chestnut soils are fertile under conditions of adequate rainfall or irrigation, but lie in a hazardous marginal belt in which years of drought and adequate rainfall are alternated. Bordering on the productive chernozem wheat belt of the Great Plains, the chestnut-soil belt of the United States offers a temptation for expanded wheat cultivation. Under special cultivation practices that conserve soil moisture, a period of moist years brings high grain yields to these marginal belts; but a series of drought years can bring repeated crop failures and poverty.
Towards still more arid regions the chestnut soils give way to the brown soils, generally similar, but with still less humus and consequently a lighter colour. In the western United States, the brown soils occupy basin in the central Rockies of Wyoming, the Colorado Piedmont.
The brown soils are typical of the middle-latitude steppes and support a light growth of grasses suitable for livestock grazing.
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